Toilets used particularly in the building and housing sectors are usually so-called standard gravity toilets. Gravity systems require large diameter sewer piping, usually with a diameter of 100 mm, and require a large amount of flush water, usually between 6-10 liters, in order to ensure flushing of the sewage collected in the gravity toilet bowl, and are further fixedly and permanently installed during the construction of a building. Standard gravity toilets are available in a multitude of designs, both for floor and wall mounted installations. The diameter of a standard gravity sewer piping can vary from country to country, but usually is within a range of 90 mm to 110 mm.
A traditional set-up for a gravity toilet arrangement (FIG. 1) includes a gravity toilet bowl 101 connected to a gravity sewer pipe 103 for discharging sewage through a water trap 102 downwards into the gravity sewer pipe based on gravity. Such toilets are either supported on the floor, whereby a flush water tank 104 with the necessary volume of about 6-10 liters is mounted on the toilet itself, or mounted to a wall, or is alternatively installed in a compartment above the toilet inside the wall. In case of a wall mounted model, normally there is a supporting frame structure inside the wall for carrying the flush water tank 104, including a water valve 105 and flush valve 106, and an activating means 108 (push button connection) for activating a flushing sequence. The large flush water tank with the arrangements for the valves and the activating means require considerable space.
For the flushing sequence, the push button is pressed, the flush valve of the flush water tank is opened, whereby the flush water flows into the toilet bowl by way of gravity and empties the collected sewage in the gravity toilet bowl into the gravity sewer pipe through the water trap also based on a normal gravity flow. Thus, in order to achieve the required flush efficiency, the flush water amount has to be about 6-10 liters as mentioned above. The large amount of flush water is necessary since the flush efficiency is based on the effect of the water flow. After the flush water tank 104 is emptied through the flush valve, the flush valve 106 is closed and the flush water tank is filled with water through the water valve 105. The filling degree is controlled by a float system (not shown), which closes the water valve at a predetermined filling degree. The float system is vulnerable and apt to malfunction and may easily cause leakage of flush water into the gravity toilet bowl. The water trap provides a water lock between the gravity toilet bowl and the gravity sewer pipe.
So-called standard vacuum toilets are used in vehicles, e.g. ships, airplanes, trains, and also in buildings. The main advantages of vacuum toilets are flexibility of installation, small diameter piping, usually a diameter about 40-50 mm, and a reduced requirement of flush water, about 1.5 liters.
A standard vacuum toilet arrangement (FIG. 2) usually includes a wall mounted vacuum toilet bowl. The vacuum toilet bowl 201 is connected to vacuum sewer piping 203 through a discharge valve 202. The operational components, including an activating means (push button connection), a control mechanism, a water valve, a discharge valve, and appropriate vacuum connections, for operating the vacuum toilet are usually assembled inside the shell of the vacuum toilet bowl or behind the vacuum toilet bowl in a service space. A vacuum toilet bowl has a specific construction and design based on its intended use in a vacuum toilet system, which most often is not found desirable in view of interior design particularly in buildings and housing.
The operation principle of a vacuum toilet arrangement is as follows. In order to activate a flushing sequence, the push button 208 is pressed, which gives a pneumatic or electric signal to the control mechanism 207, which opens the discharge valve 202 and the flush water valve 206, which normally is directly connected to a line 204 of pressurized water for providing flushing water. After a timed flushing sequence, the discharge valve 202 is closed. After a given delay, the flush water valve 206 is closed, whereby a small amount of water is allowed to form in the toilet bowl 201. The vacuum needed for operation of the vacuum toilet system is generated by a vacuum unit 209.
Examples of vacuum toilet arrangements can be found e.g. in CN 102561488, U.S. Pat. No. 6,085,366 and EP 1 840 242.
Due to the operational criteria, standard vacuum toilets require a specific type of vacuum toilet bowl, which on one hand is practical in view of standard fabrication, but which on the other hand limits the design and installation freedom.
Vacuum toilet arrangements also generate considerable noise in connection with a flushing sequence. U.S. Pat. No. 4,928,326 discloses an arrangement for lessening the discharge noise, however, resulting in a surplus energy consumption due to an excessive suction of air into the vacuum sewer piping. Attempts have also been made to seal the lid of the vacuum toilet bowl, which again results in a loss of discharge effect due to a lessening of the pressure difference.
Due to the advantages of a vacuum toilet arrangement, there have been attempts to provide a combination of a gravity toilet arrangement and a vacuum sewage system, i.e. providing a gravity toilet with a vacuum sewage connection.
This has been done by connecting a gravity toilet bowl 301, including a standard so-called gravity flushing arrangement with a large (discussed above) flush water tank 304, a water valve 305, a flush valve 306, an activating means 308, and a water trap (not shown; corresponding to reference numeral 102 of FIG. 1), to a vacuum sewage system (FIG. 3). The gravity toilet bowl 301 deploys a gravity flushing arrangement as described above in connection with FIG. 1, whereby the outlet of the gravity toilet bowl 301 is connected to a vacuum interface unit 310 by means of the water trap (not shown), whereby the vacuum interface unit 310 in turn is connected to vacuum sewer piping 303 through a discharge valve 302. The interface unit, which functions as and intermediate collection tank, is dimensioned to receive a number of standard gravity flushes from the gravity toilet bowl, which necessitates a substantial volume. The filling degree of the vacuum interface unit 310, which thus functions as an intermediate waste tank, is controlled by means of an activator unit 311. When a predetermined filling degree of the vacuum interface unit 310 has been reached, the activator unit 311 activates the discharge valve 302 for discharging the contents of the vacuum interface unit into the vacuum sewer piping 303. The vacuum needed for operation of the vacuum sewage connection is generated by a vacuum unit 309.
First of all, such an installation requires two separate systems, a gravity system and a vacuum sewage system with separate operational circuits. The combination of the known systems additionally necessitates an interface unit, i.e. an intermediate waste tank, in which sewage received from the gravity toilet bowl is collected and temporarily stored. The interface unit is closed off towards the toilet bowl by means of a water trap and towards the vacuum sewer piping by means of a vacuum discharge valve.
Secondly, the interface unit requires considerable space and thus cannot be installed for easy access, e.g. above the toilet bowl. As a consequence, the vacuum discharge valve is also not easily accessible.
Thirdly, as in a traditional gravity toilet system, the amount of flush water is large, about 6-10 liters as discussed above. This is not advantageous for a vacuum sewage system, which is designed to transport small discrete slugs of sewage with volumes of air on both sides having a rising vacuum level in a downstream direction. As a consequence, the transport efficiency of the vacuum sewage system is considerably decreased. In addition this solution also creates odor problems because the vacuum interface unit is ventilated to the atmosphere in order to discharge the vacuum interface unit into the vacuum sewer piping.